In the case of Agnello et al. v. United States, the U.S Supreme Court ruled that evidence obtained through an illegal search and seizure could not be used in federal courts as it violated Fourth Amendment rights. The defendants were convicted for conspiracy to violate narcotic laws based on evidence found during a warrantless search of their homes following their arrest at another location. The court held that while officers had probable cause to arrest and search the defendants at the place they were arrested, this did not justify subsequent searches of their residences without warrants. This decision established important precedent regarding protection against unreasonable searches and seizures.

In the dissenting opinion for Agnello et al. v. United States, Justice Oliver Wendell Holmes Jr., joined by Justice Louis Brandeis, argued that the Fourth Amendment's protection against unreasonable searches and seizures was violated in this case. They contended that evidence obtained through an illegal search should not be admissible in court as it infringes upon a person’s constitutional rights. The majority ruling allowed for such evidence to be used if it directly linked the defendant to the crime charged; however, Justices Holmes and Brandeis believed this interpretation of law could lead to potential abuses of power by law enforcement officials who might conduct unlawful searches with impunity under pretextual reasons related to a criminal investigation.